Liquid glyphosate formulations that include efficacy-enhancing surfactants are widely used to control weeds. Such formulations have been described in U.S. Pat. Nos. 4,507,250, 4,481,026, 4,405,531, 4,315,765, 4,140,513, 3,977,860, 3,853,530 and 3,799,758. Such formulations generally comprise a glyphosate salt, for example the isopropylammonium salt, and an efficacy-enhancing surfactant, for example tallowamine ethoxylate.
The recent development of solution concentrates of glyphosate has involved the identification of salts and surfactants that enable higher levels of glyphosate ae to be provided in a given volume without loss of efficacy relative to well-established glyphosate formulations (eg Roundup made by Monsanto).
The achievement of higher loading glyphosate formulations is important because:                in a highly competitive market, farmers will pay a premium for the product which contains the highest loading of glyphosate, and        a given quantity of glyphosate ae can be transported and stored in a more compact container if the loading of glyphosate ae in the formulation (on a volume basis) is higher—this has been extensively discussed in U.S. Pat. No. 6,544,930 (Wright, filed 2001, assigned to Monsanto).        
The following methods for increasing the loading of glyphosate ae in a formulation have been proposed.
In U.S. Pat. No. 5,998,332 (Sato et al, filed 1998, assigned to Monsanto) there is described an aqueous herbicidal composition comprising an ammonium salt of glyphosate in an amount between 10-50% ae by weight. It is stated that there is a difficulty in defining suitable surfactants for use with sodium glyphosate in a liquid formulation. Example 1 in this application provides a method of formulating liquid glyphosate at 470 ae g/L in a formulation that includes surfactant. Example 4 provides a method for formulating liquid glyphosate at 540 ae g/L in the presence of surfactant.
In U.S. Pat. No. 6,277,788 (Wright, filed 1999, assigned to Monsanto) there is described a herbicidal composition comprising glyphosate predominantly in the form of the monoethanolammonium salt in an amount of about 360 to 570 ae g/L. In the discussion associated with Table 7 in this application, it is stated that at the extremely high glyphosate concentrations of 540 ae g/L, there is scope for including sufficient surfactant to provide commercially acceptable herbicidal efficacy. Appropriate surfactants for use in these formulations include polyoxyethylene (5) cocoamines.
In U.S. Pat. No. 6,544,930 (Wright, filed 2001, assigned to Monsanto) there is described a storage and shipping system comprising a container substantially filled with an aqueous solution of glyphosate, predominantly in the form of one or a mixture of potassium and monoethanolammonium (MEA) salts thereof, the solution having a glyphosate ae concentration of at least 30%. In the text associated with Table 6 in this application, it is stated that a composition that contains glyphosate ae at a loading as high as 540 ae g/L is a significant advance in the art that could not have been predicted from prior knowledge of the surfactant or of glyphosate MEA salt.
In U.S. Pat. No. 7,049,270 (Lennon et al, filed 2001, assigned to Monsanto) there is described a formulation useful in retarding the growth of vegetation comprising an aqueous mixture containing a surfactant, glyphosate primarily as potassium salt, and a dicarboxylic acid. In the examples of this specification, the highest loading of glyphosate in a formulation also comprising surfactant appears to be 542 ae g/L.
In WO 2006/023431, corresponding to PCT/US2005/028930 (Eaton et al, assigned to Monsanto) it is stated that there is an especial need for formulations having high glyphosate loadings. This application teaches: a mixed salt aqueous glyphosate formulation where the glyphosate concentration is not less than 360 ae g/L, wherein (a) the glyphosate is in anionic form accompanied by low molecular weight non-amphiphilic cations in a total molar amount of about 100% to 120% of the molar amount of glyphosate; (b) said cations comprise potassium and propylammonium cations in a mole ratio of 70:30 to 90:10 and (c) said potassium and propylammonium cations together consisting of all low molecular weight non-amphiphilic cations in the composition. In table 2 which is associated with example 2 in the application, two formulations are described in which target concentrations of glyphosate are said to be 600 ae g/L. A footnote to the table explains that in fact the achieved concentration of glyphosate in these formulations was 590 ae g/L, due to raw material concentration limits.
The above literature shows that in spite of significant effort by a well-resourced multi-national company, the maximum level of glyphosate that can be incorporated in an aqueous formulation comprising efficacy-enhancing surfactant is 590 ae g/L.
U.S. Pat. No. 6,747,164 (Gustasson and Weuste, filed 2001, assigned to Akzo Nobel) describes amine compounds with improved biodegradability as adjuvants for pesticides and fertilisers. The amino compound is an esteramine or amidoamine surfactant. The enteramines are obtained from an ethoxylated alcohol that has been carboxymethylated and then esterified with a tertiary hydroxyamine (alkanolamine), and the amidoamines are obtained by a reaction between a fatty acid or a fatty acid methyl ester and a diamine, such as N,N-bishydroxyethyl-1,3 propylenediamine. Claim 12 in this specification notes the use of these adjuvants with glyphosate or glyphosate salts. There is no reference in this patent to high-loading formulations of glyphosate.
U.S. Pat. No. 6,881,707 (Howat and Hay, assigned to Nufarm) describes a glyphosate composition comprising a mixture of salts of glyphosate comprising each of potassium and isopropylammonium salts. None of the formulations in this application has a loading of glyphosate in excess of 500 ae g/L, and there is no suggestion in this specification that high glyphosate loadings can be achieved using the teachings provided. Furthermore the specification asserts that the use of specific combinations of low molecular weight non-amphiphilic cations leads to a significant improvement in the bioefficacy of the glyphosate composition.
There is an ongoing need to provide higher-loading liquid glyphosate formulations which comprise efficacy-enhancing surfactants.